#! /bin/sh

ver=1.0

use() {
    cat <<END
Use:
    `basename $0` [-n] n1[-n2][,...] [file]
e.g.
    `basename $0` 23-60,100-140,300-390 myfile
    
Prints lines n1-n2, ... from a file.
If no filename is given, stdin is used.

Options:
    -n	prefix each line with its line numbers from the input stream.
END
}

number=no
while [ $# -gt 0 ] ; do
    case "$1" in
    -n ) number=yes ; shift ;;
    -* ) use ; exit 1 ;;
    * ) break ;;
    esac
done

case $# in 1 | 2 ) ;; * ) use ; exit 1 ;; esac

findcommand() {
    type "$1" 2>/dev/null | awk '$2 != "not" {print $NF}'
}
AWK=`findcommand gawk`
test "$AWK" = "" && AWK=`findcommand mawk`
test "$AWK" = "" && AWK=`findcommand nawk`
test "$AWK" = "" && AWK=`findcommand awk`

linelist=`echo "$1" |
    $AWK -F, '
    { for (i=1; i<=NF; i++) {
	    n = split($i, x, "-")
	    printf("-e %d,%dp ", x[1], (n == 1) ? x[1] : x[2]);
	}
    }'`
shift	; # discard the line list from the command-line.

case $number in
yes ) awk '{print NR, $0}' "$@" | sed -n $linelist ;;
* ) sed -n $linelist "$@" ;;
esac